Remove dependency on request object in JWT producers (bug #983824)

- Remove request as argument to _prepare_pay and _prepare_pay_inapp
- Modify tests to talk directly to JWT producers
- Remove request dependent logic from JWT producer and move into view
- Update views to unpack request object and pass data directly into JWT producers
Merge pull request #1867 from JaredKerim-Mozilla/983824

Remove dependency on request object in JWT producers (bug #983824)